Methods &amp; compositions for stabilizing catalytic processes

ABSTRACT

Methods and compositions for stabilizing the activity of catalytic compositions during catalytic processes, such as alkylation. A catalytic composition comprising a partially deactivated ionic liquid catalyst may be regenerated by reaction with a metal to form reactivated catalyst and an inorganic catalyst precursor; and the catalytic composition may be amended in-process by addition of an organic catalyst precursor for reaction with the inorganic catalyst precursor to form fresh ionic liquid catalyst. The organic catalyst precursor may be protected from water, e.g., during handling, by hydrophobic material(s).

FIELD OF THE INVENTION

The present invention relates to methods and compositions forstabilizing catalytic processes.

BACKGROUND OF THE INVENTION

Alkylation processes for the production of high octane gasoline cutshave been driven by the increasing demand for high quality and cleanburning gasoline. Alkylate gasoline, which currently constitutes about14% of the gasoline pool, is typically produced by alkylating isobutanewith low-end olefins. Conventional alkylation processes use eithersulfuric acid or hydrofluoric acid as catalyst, both of which have anumber of drawbacks.

Disadvantages associated with the use of H₂SO₄ as an alkylation catalystinclude the vast quantities of acid required to initially fill thereactor, and the large amounts of spent acid to be withdrawn on a dailybasis for off-site regeneration, which involves incinerating the spentacid and preparing fresh acid. Disadvantages associated with the use ofHF as an alkylation catalyst include the special handling requirementsdue to the highly corrosive nature of the acid, and the formation ofaerosols, which presents an environmental and safety risk. These risksare evident from the additional safety measures associated with modernHF alkylation processes, such as water spray and catalyst additive foraerosol reduction.

Accordingly, catalyst systems that are safer and more environmentallyfriendly than HF and H₂SO₄ are required for refinery alkylationprocesses. However, thus far, no viable replacement catalyst systemshave been commercialized, despite extensive research in both academicand industrial institutions.

Ionic liquids are liquids that are composed entirely of ions. Fused saltcompositions are a class of ionic liquids that are liquid at lowtemperatures, with melting points often below room temperature. Ingeneral, such compositions have found applications as catalysts,solvents and electrolytes. The most common ionic liquids are thoseprepared from organic cations (ammonium, phosphonium, and sulphonium)and inorganic or organic anions. Anions of ionic liquids include BF₄ ⁻,PF₆ ⁻, haloaluminates such as Al₂Cl₇ ⁻ and Al₂Br₇ ⁻, [(CF₃SO₂)₂N)]⁻,alkyl sulfates (RSO₃ ⁻), carboxylates (RCO₂ ⁻). The most interestingionic liquids for acid catalysis are those derived from organic halidesalts and Lewis acids (such as AlCl₃, TiCl₄, SnCl₄, FeCl₃, etc).Chloroaluminate ionic liquids are perhaps the most commonly used ionicliquid catalyst systems for acid-catalyzed reactions.

Chloroaluminate ionic liquids can be prepared, for example, from analkylpyridinium chloride or alkylimidazolium chloride and a metalhalide. The use of the fused salts (1-alkylpyridinium chloride andaluminum trichloride) as electrolytes is discussed in U.S. Pat. No.4,122,245. Other patents which discuss the use of fused salts aselectrolytes include U.S. Pat. Nos. 4,463,071 and 4,463,072. Ionicliquids and their methods of preparation are also disclosed in U.S. Pat.Nos. 5,731,101; 6,797,853; 5,104,840 and in US Patent ApplicationPublication Nos. 2004/0077914 and 2004/0133056.

During the past decade, the emergence of chloroaluminate ionic liquidshas sparked some interest in AlCl₃-catalyzed alkylation in ionic liquidsas a possible alternative to conventional catalysts. For example, thealkylation of isobutane with butenes and ethylene in ionic liquids hasbeen described in U.S. Pat. Nos. 5,750,455; 6,028,024; and 6,235,959 andin the Journal of Molecular Catalysis, 92 (1994), 155-165; “IonicLiquids in Synthesis”, P. Wasserscheid and T. Welton (eds.), Wiley-VCHVerlag, 2003, pp 275). U.S. Pat. No. 7,531,707 to Harris et al.discloses a process for the alkylation of light isoparaffins witholefins using an ionic liquid catalyst and an alkyl halide promoter.

As a result of their use in catalytic reactions, ionic liquids becomedeactivated and may eventually need to be replaced. However, ionicliquid catalysts are expensive and replacement adds significantly tooperating expenses by, in some cases, requiring shutdown of anindustrial process. One of the heretofore unsolved problems impeding thecommercialization of chloroaluminate ionic liquid catalysts has been theinability to effectively and efficiently regenerate and recycle them.

Recently, methods for ionic liquid catalyst regeneration were disclosedin US Patent Application Pub. No. 2007/0249485 (Elomari, et al.), inwhich spent ionic liquid catalyst, in combination with conjunct polymer,was reactivated by treatment with a regeneration metal. A consequence ofthis treatment is that excess metal halide may accumulate in the ionicliquid during catalyst regeneration. US Patent Application Pub. No.2009/0163349 (Elomari, et al.), discloses the removal of excess metalhalide from an ionic liquid catalyst by the addition of either anorganic halide salt or a mixed salt, corresponding to the ionic liquidcatalyst, having a metal halide/organic halide salt molar ratio lessthan two.

There is a need for methods for the regeneration of spent ionic liquidcatalysts wherein the composition of the catalyst can be efficiently andeconomically maintained during and/or after catalyst regeneration. Thereis a further need for ionic liquid catalyzed alkylation processeswherein the catalytic activity and composition of the ionic liquidcatalyst is stabilized in an economic and efficient manner.

SUMMARY OF THE INVENTION

The present invention is directed to methods for stabilizing catalyticactivity and catalytic compositions during catalytic processes, such ashydrocarbon alkylation processes catalyzed by ionic liquid catalysts,wherein the catalysts may be prepared in-process from hygroscopic saltswithout introducing water into the catalytic compositions. The presentinvention is further directed to novel compositions comprising ahygroscopic catalyst precursor or component of an ionic liquid catalyst,wherein the hygroscopic catalyst precursor is protected from moisture bya water-resistant coating or water-impervious barrier material.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment, the present invention provides methods forstabilizing a catalytic composition, wherein a hygroscopic catalystprecursor is added, in-process, to the catalytic composition in anamount effective to control the catalytic activity of the catalyticcomposition, and wherein the catalyst precursor may be at leastpartially encapsulated within a hydrophobic material prior to theaddition of the catalyst precursor to the catalytic composition.

The present invention also provides alkylation processes using an ionicliquid catalyst for alkylating an isoparaffin with an olefin in analkylation zone in which the alkylate product is separated from theionic liquid, and a portion of the ionic liquid is regenerated in aregeneration zone to provide reactivated catalyst and an “excess” of ametal halide, wherein an organic halide salt may be added to theregeneration zone for reaction with the excess metal halide to form theionic liquid catalyst de novo. The organic halide salt may be referredto herein as a first catalyst precursor, and the metal halide may bereferred to herein as a second catalyst precursor.

The present invention further provides compositions comprising ahygroscopic catalyst precursor for addition to the catalytic compositionbefore, during, or after catalyst regeneration, or during an alkylationprocess that includes catalyst regeneration, wherein the catalystprecursor may be at least partially encapsulated within a hydrophobicmaterial prior to the addition of the catalyst precursor to thecatalytic composition.

Apart from environmental, health, and safety considerations, ionicliquid alkylation catalysts offer numerous advantages over conventionalcatalysts (H₂SO₄ and HF), including: lower capital expenditure ascompared to H₂SO₄ and HF alkylation plants; lower operating expendituresas compared to H₂SO₄ alkylation plants; reduction in catalyst inventoryvolume (potentially by 90%); reduction in catalyst make-up rate(potentially by 98% compared to H₂SO₄ plants); higher gasoline yield;comparable or better product quality; expansion of alkylation feeds toinclude isopentane and ethylene; and higher catalyst activity andselectivity. Alkylation processes using ionic liquid catalysts aredisclosed, for example, in commonly assigned U.S. Pat. No. 7,531,707 toHarris et al., the disclosure of which is incorporated by referenceherein in its entirety.

As noted hereinabove, ionic liquid catalysts may become deactivatedduring use. For example, in an alkylate production unit, light (e.g.,C₂-C₅) olefin and isoparaffin feeds may be contacted in the presence ofa catalyst that promotes the alkylation reaction. In an embodiment ofthe present invention, the catalyst is a chloroaluminate ionic liquid.The reactor produces a biphasic mixture of alkylate hydrocarbons,unreacted isoparaffins, and ionic liquid catalyst containing someconjunct polymers. The more dense catalyst/conjunct polymer phase may beseparated from the hydrocarbons by gravity settling in a decanter. Thiscatalyst may be partially deactivated by the binding of the conjunctpolymer to AlCl₃. The spent catalyst can be regenerated or reactivatedby contact with a suitable regeneration metal, such as B, Al, Ga, In,Tl, Zn, Cd, Cu, Ag, Au, and mixtures thereof. The regeneration metal maybe selected on the basis of the composition of the particular catalystto prevent contamination of the catalyst with unwanted metal complexesor intermediates. For example, aluminum metal will be the metal ofchoice for the regeneration of chloroaluminate ionic liquid catalysts.

The products of the catalyst regeneration step include reactivatedcatalyst and removable conjunct polymers, among others, as describedherein. The conjunct polymers can be separated from the reactivatedionic liquid catalyst, for example, by solvent extraction, decantation,and filtration. In one embodiment, a used ionic liquid catalyst/conjunctpolymer mixture is introduced continuously into a regeneration reactor(or zone) containing a regeneration metal. Inert hydrocarbons, in whichconjunct polymers are soluble, are fed into the reactor at the desiredrate. The inert hydrocarbons may be a normal hydrocarbon ranging fromC₃-C₁₅ or their mixtures, and usually C₄-C₈. The residence time,temperature, and pressure of the reactor will be selected to allow thedesired reactivation of the ionic liquid catalyst.

The reaction product is withdrawn and sent to a separator to provide twostreams: one comprising inert hydrocarbons together with removableconjunct polymers, and the other stream comprising regenerated ionicliquid catalyst. A gravity decanter may be used to separate the mixture,from which the more dense ionic liquid phase is withdrawn. Thereactivated ionic liquid catalyst may be returned to the alkylationreactor. The solvent/conjunct polymer mix may be distilled to recoverthe solvent. Various modifications of this process are also within thescope of the present invention.

During the regeneration of, for example, a spent chloroaluminate ionicliquid catalyst using aluminum metal, aluminum trichloride is producedas part of the regeneration chemistry. Aluminum trichloride is a solidwhich can precipitate and accumulate in the regeneration zone or otherparts of the system. Using 1-butylpyridinium chloroaluminate as anon-limiting example of an ionic liquid catalyst, a suitableAlCl₃/1-butylpyridinium chloride molar ratio is two. In order tostabilize processes of the present invention by using a regulatedcatalyst inventory, it is necessary to effectively manage the “excess”aluminum trichloride formed during catalyst regeneration.

As noted hereinabove, metal halide formed during ionic liquid catalystregeneration can be accommodated by the addition of either i) thecorresponding organic halide catalyst precursor (a hygroscopic solid),or ii) a mixed salt (ionic liquid) corresponding to the ionic liquidcatalyst but having a (lower) metal halide/organic halide salt molarratio less than two (the ionic liquid catalyst itself has a metalhalide/organic halide salt molar ratio of two). Handling a hygroscopicsolid (organic halide catalyst precursor) (option i)) is generally lessconvenient and less inefficient than handling an ionic liquid (optionii). However, in order to obtain a desired metal halide/organic halidesalt molar ratio of two (2) using an ionic liquid mixed salt make-upstream having a metal halide/organic halide salt molar ratio of, e.g.,1.8, would require a large volume of the regenerated catalyst to bereplaced with the make-up stream. Such a scheme, involving the removaland replacement of large volumes of ionic liquid, is very inefficient,expensive, and wasteful. From a theoretical standpoint, reacting theexcess metal halide with the organic halide catalyst precursor is a muchmore efficient mechanism for restoring the desired metal halide/organichalide salt molar ratio. However, in practice, handling a hygroscopicsalt, which rapidly accumulates atmospheric moisture to form a stickypaste or solution, is problematic. Even using a lock hopper under inertatmosphere for adding the hygroscopic solid (organic halide catalystprecursor), the solid would still be exposed to air when the lock hopperwas loading, and this presents the likelihood of water accumulation bythe solid and the introduction of water into the catalyst system.

According to one aspect of the present invention, the addition of (ahygroscopic) organic halide catalyst precursor for accommodating the“excess” metal halide may be enabled by preventing water uptake by thecatalyst precursor prior to addition of the catalyst precursor to thecatalytic composition. In an embodiment, water uptake by the catalystprecursor can be prevented by a hydrophobic coating material disposed onthe catalyst precursor prior to addition of the catalyst precursor tothe catalytic composition.

In an embodiment, the organic halide catalyst precursor (e.g.,1-butylpyridinium chloride) may be added to the catalyst compositionafter treatment of the catalytic composition with the regenerationmetal. In this case, the amount of metal halide (e.g., AlCl₃) producedduring regeneration of the ionic liquid catalyst can be quantified bymeasuring the consumption of Al metal; then, an amount of organic halidecatalyst precursor needed to react with the excess aluminum trichloridecan be determined. In another embodiment, the organic halide catalystprecursor may be added to the catalyst composition prior to, orconcurrently with, treatment of the catalytic composition with theregeneration metal. Regardless of when the catalyst precursor is addedto the catalytic composition, the metal halide (e.g., AlCl₃) may combinewith the added organic halide catalyst precursor in the de novoformation of the ionic liquid (e.g., chloroaluminate) catalyst.

A first catalyst precursor, to be added to a catalytic compositionduring or after catalyst regeneration, may comprise a hydrocarbyl, e.g.,alkyl, substituted pyridinium halide, imidazolium halide,tetraalkylammonium halide, or trialkylammonium hydrohalide. As anexample, the first catalyst precursor may be a salt of the generalformulas A, B, C, and D:

wherein X is halide, each of R, R₁, and R₂=H, methyl, ethyl, propyl,butyl, pentyl or hexyl, wherein R₁ and R₂ may or may not be the same;and each of R₃, R₄, R₅, and R₆=methyl, ethyl, propyl, butyl, pentyl orhexyl, wherein R₃, R₄, R₅, and R₆ may or may not be the same.

The first catalyst precursor may be a hygroscopic solid, such as analkyl substituted pyridinium halide or an alkyl substituted imidazoliumhalide. Accordingly, absent the present invention, the first catalystprecursor may be difficult or impossible to handle per se withoutrisking water uptake by the catalyst precursor and the introduction ofwater into the catalyst system. According to one aspect of the presentinvention, a hydrophobic coating may be disposed on at least a portionof the first catalyst precursor prior to addition of the first catalystprecursor to the catalytic composition in the regeneration zone.Typically, the hydrophobic coating may completely surround, orencapsulate, the first catalyst precursor. The hydrophobic coating maybe selected to repel water and to decrease or eliminate water adsorptionby the catalyst precursor.

In an embodiment, the hydrophobic coating may comprise a wax, an oil, aresin, or a polymer, and the like. Hydrophobic materials that may besuitable for coating the first catalyst precursor include, withoutlimitation, petroleum-derived waxes (paraffin wax), as well as waxesderived from plants, insects, or other organisms; mineral oils, as wellas various vegetable oils, and the like; natural and synthetic resins;and natural or synthetic polymers, or their derivatives, and mixturesthereof. In an embodiment, the hydrophobic coating may comprise amaterial that lacks a Lewis base group, e.g., carbonyl, such as asaturated wax or paraffin. The invention is not limited to anyparticular hydrophobic coating material(s).

In an embodiment of the present invention, the first catalyst precursormay be added to the catalytic composition (e.g., in the regenerationzone) while the catalyst precursor is coated with the hydrophobicmaterial. In other embodiments, the hydrophobic material may be at leastpartially removed from the catalyst precursor prior to addition of thecatalyst precursor to the catalytic composition, e.g., just prior toaddition of the catalyst precursor to the regeneration zone from a lockhopper under an inert atmosphere.

In an embodiment, the hydrophobic coating may comprise a material thatis at least partially removed from the catalyst precursor when thecoated catalyst precursor is exposed to process conditions, such ascatalyst regeneration conditions. In one embodiment, the coating may beremoved from the catalyst precursor by melting the hydrophobic material.

In an embodiment, the hydrophobic material/coating on the first catalystprecursor may comprise a wax selected for having a melting point withina particular temperature range. For example, the melting point of thehydrophobic material may be selected according to the conditions towhich a coated catalyst precursor may be exposed before, during, orafter catalyst regeneration. The melting point of the hydrophobicmaterial may also be selected, in part, according to the conditionsunder which the coated catalyst precursor, e.g., coated granules ofcatalyst precursor, is to be stored and/or transported. In anembodiment, the hydrophobic material may have a melting point less thanabout 125° C., and typically less than about 100° C. In anotherembodiment, the hydrophobic material may have a melting point in therange from about 40° C. to about 95° C.

In an embodiment, the hydrophobic coating may comprise a C₁₆-C₃₀paraffin wax. The hydrophobic coating may melt under catalystregeneration conditions, and the hydrophobic material may besubsequently extracted from an ionic liquid catalytic composition, e.g.,using a C₃-C₁₅ hydrocarbon. In an embodiment, the hydrophobic coatingmaterial may be extracted from a regeneration reactor, together withconjunct polymer, e.g., using butanes from a debutanizer.

In an embodiment, the first catalyst precursor may be coated with thehydrophobic coating by a) suspending dry catalyst precursor in moltenhydrophobic material to form an aggregate material, and b) forming theaggregate material into a suitable shape. For example, the moltenhydrophobic material, with suspended catalyst precursor therein, may beallowed to solidify prior to extrusion of encapsulated catalystprecursor.

In another embodiment, the dried catalyst precursor (anhydrous) may bepelletized, i.e., formed into a pellet, granule, or the like, prior tothe application of hydrophobic coating material thereto. In anembodiment, pellets of the catalyst precursor may be coated with wax toprovide moisture resistant granules of the catalyst precursor. Thehydrophobic coating may be applied to pellets of the catalyst precursorby spraying the coating on each of the pellets. Alternatively, thehydrophobic coating may be applied to the catalyst precursor by dippingeach of the pellets in molten hydrophobic coating material. Othermethods for applying hydrophobic materials to the first catalystprecursor are also within the scope of the present invention.

In an embodiment, coated pellets or granules of catalyst precursor mayfurther comprise an additive such as a flow agent and/or an anti-cakingagent, for example, to improve the handling characteristics (e.g.,flowability) of the coated pellets. The pellets of catalyst precursormay be at least substantially uniform in size and/or shape. Suchuniformity in size and/or shape may simplify handling, storage, andtransportation of the granules. Coated pellets or granules comprisingcatalyst precursor may be formed into various shapes, for example,rounded, flattened, spheroidal, disc-like, cylindrical, pyramidal,amorphous, square, oblong, or irregular in shape.

As noted hereinabove, the catalyst precursor may be hygroscopic and thehydrophobic coating may effectively prevent the uptake of water by thecatalyst precursor during storage and/or prior to use of the coatedcatalyst precursor. As a non-limiting example, the hydrophobic coatingmay prevent any substantial uptake of water by the catalyst precursorwhen the coated catalyst precursor is exposed for a period of at least 5days to conditions, e.g., storage conditions, including a temperature upto about 40° C. and up to about 95% relative humidity.

According to one aspect of the present invention, there is provided amethod for stabilizing a catalytic composition comprising an ionicliquid. In an embodiment, the ionic liquid catalyst may comprise achloroaluminate ionic liquid catalyst, e.g., for catalyzing thealkylation of an isoparaffin with an olefin. A method for stabilizing acatalytic composition may be performed in-process, e.g., during or aspart of a catalyst regeneration process or an alkylation process. Theterm “in-process” may be used herein to refer to one or more steps,acts, or reactions that occur during a process of which the step(s),act(s), or reaction(s) may be a part, or in which the step(s), act(s),or reaction(s) may be involved.

In an embodiment, a method for stabilizing a catalytic composition mayinvolve the addition of a hygroscopic first catalyst precursor to acatalytic composition in an amount effective to control or manage thecatalytic activity of the catalytic composition. The first catalystprecursor may comprise an organic halide salt that reacts with thesecond catalyst precursor (metal halide) to form new ionic liquidcatalyst. The first catalyst precursor may be added to the catalyticcomposition before, during, or after regeneration of the catalyticcomposition, e.g., before, during, or after treatment of the catalyticcomposition with regeneration metal, as described hereinabove. In anembodiment, the regeneration metal may comprise Al metal, e.g.,substantially as described in commonly assigned U.S. patent applicationSer. Nos. 11/408,336 and 11/960,319 (US Pub. Nos. 2007/0249485 and2009/0163349, respectively), the disclosures of which are incorporatedby reference herein in their entirety.

During regeneration of the ionic liquid catalyst by treatment with Almetal, “excess” AlCl₃ may be formed, e.g., by reaction of Al with thechlorine-containing conjunct polymer component of the spent catalyst. Inorder to stabilize the catalyst composition and to control the catalyticactivity of the ionic liquid, the AlCl₃ may be “removed” by adding theorganic halide catalyst precursor, thereby forming fresh ionic liquidcatalyst. That is to say, during processes for catalyst stabilizationaccording to the present invention, an additional quantity of the ionicliquid catalyst may be formed de novo. The additional ionic liquidcatalyst thus formed may be fed to the alkylation zone, or theadditional ionic liquid catalyst may be stored for future use.

According to one aspect of the present invention, the first catalystprecursor is at least partially encapsulated within a hydrophobicmaterial prior to the addition of the catalyst precursor to thecatalytic composition. In an embodiment, the catalyst precursor may becoated with the hydrophobic material at the time of addition of thecatalyst precursor to the catalytic composition. For example, catalystprecursor that has been coated with the hydrophobic material may beadded to the catalyst composition in the regeneration zone underregeneration conditions that are conducive to removal of the hydrophobiccoating from the catalyst precursor. In an embodiment, the regenerationzone may be at a temperature equal to or greater than (≧) the meltingpoint of the hydrophobic material. In a non-limiting example, thehydrophobic material may have a melting point less than 60° C., and theregeneration conditions may include a temperature of at least 90° C.Hydrophobic coating materials and coated catalyst precursor compositionssuitable for use in methods and processes of the present invention aredescribed hereinabove. As an example, the first catalyst precursor maycomprise a salt of the general formulas A, B, C, and D, supra, and thefirst catalyst precursor may be coated with a wax or an oil, and thelike.

An ionic liquid catalyst for alkylation processes according to thepresent invention may be prepared by contacting the first catalystprecursor (an organic halide salt) with a metal halide. The organichalide salt may be referred to herein as the first (or organic) catalystprecursor, and the metal halide may be referred to as the second (orinorganic) catalyst precursor. The organic halide salt may be, forexample, an alkylpyridinium chloride or an alkylimidazolium chloride,and the metal halide may be, for example, aluminum trichloride (AlCl₃).The ionic liquid catalyst may be prepared by combining the organichalide salt with AlCl₃ in an AlCl₃/organic halide salt molar ratio oftwo. In a particular non-limiting example, an ionic liquid catalyst ofthe invention may comprise 1-butylpyridinium heptachloroaluminate (see,for example, commonly assigned U.S. Pat. No. 7,495,144, the disclosureof which is incorporated by reference herein in its entirety).

In an embodiment, the first catalyst precursor is added to the excessAlCl₃/regenerated catalytic composition in an amount sufficient toprovide an AlCl₃/organic catalyst precursor molar ratio of about two,such that at least substantially all of the AlCl₃ formed during catalystregeneration is consumed in forming fresh ionic liquid catalyst. Anyhydrophobic material released from the coated catalyst precursor intothe ionic liquid may be removed, for example, together with conjunctpolymer released during catalyst regeneration, by extraction of thecatalyst composition with one or more hydrocarbons, e.g., a C₃-C₁₅hydrocarbon or their mixtures, and typically C₄-C₈, in which thehydrophobic material (and conjunct polymer) are soluble.

As a non-limiting example, a process according to an embodiment of thepresent invention may involve separating a partially spent ionic liquidcatalyst from a hydrocarbon phase containing an alkylate product. Afirst portion of the partially spent catalyst may be returned to thealkylation zone to participate in further alkylation reactions. A secondportion of the partially spent catalyst may be fed to a regenerationzone for regenerating the partially spent ionic liquid catalyst. Thepartially spent catalyst may include a certain amount of conjunctpolymer bound to the ionic liquid. In the regeneration zone, thepartially spent catalyst may be contacted with a regeneration metalunder regeneration conditions to provide a catalytic compositioncomprising i) reactivated ionic liquid catalyst and ii) free conjunctpolymer, wherein AlCl₃ is formed by reaction of the regeneration metalwith the partially spent catalyst. By “free conjunct polymer” is meantconjunct polymer that has been released from spent catalyst (e.g., byreaction with Al metal), and/or conjunct polymer that can be readilyextracted from the ionic liquid phase using hydrocarbon solvents. TheAlCl₃ formed during catalyst regeneration may be contacted with theadded first catalyst precursor to form fresh ionic liquid catalyst.Substantially all of the AlCl₃ formed during catalyst regeneration mayreact with the first catalyst precursor when the latter is added to thecatalytic composition in an amount sufficient to provide an AlCl₃/firstcatalyst precursor molar ratio of about two.

Prior to the addition of the first catalyst precursor to the catalyticcomposition, the catalyst precursor may be coated with a hydrophobicmaterial sufficient to prevent moisture uptake by the catalystprecursor. The invention is not limited to addition of the firstcatalyst precursor to the catalytic composition at any particular pointor stage of the regeneration reaction or process. For example, anorganic halide catalyst precursor may be added to the catalyticcomposition prior to, concurrently with, or subsequent to treatment ofthe catalytic composition with the regeneration metal.

The present invention further provides an alkylation process for theproduction of high quality gasoline blending agents, e.g., from refineryprocess streams. In an embodiment, a process for forming an alkylate maycomprise contacting under alkylation conditions at least one C₂ to C₆olefin and at least one C₃ to C₆ isoparaffin with an ionic liquidcatalytic composition prepared from a hygroscopic first catalystprecursor, wherein the first catalyst precursor is added in-process tothe catalytic composition and the catalyst precursor is at leastpartially coated with a hydrophobic material prior to addition of thecatalyst precursor to the catalytic composition. The catalyticcomposition may comprise an acidic ionic liquid catalyst. In anembodiment, the ionic liquid may comprise a chloroaluminate prepared bycontacting the first (organic) catalyst precursor with the second(inorganic) catalyst precursor, substantially as described hereinaboveor as described in Example 1 (infra). The catalytic composition mayfurther comprise an alkyl halide and an HCl co-catalyst.

As a non-limiting example, the ionic liquid catalyst may be prepared bycontacting 1-butylpyridinium (first catalyst precursor) with AlCl₃(second catalyst precursor) in an AlCl₃/first catalyst precursor molarratio of two, to form 1-butylpyridinium heptachloroaluminate. Otherexamples of acidic ionic liquid catalysts which may be useful inpracticing the present invention include 1-butyl-4-methylpyridiniumchloroaluminate, 1-butyl-3-methyl-imidazolium chloroaluminate, and1-H-pyridinium chloroaluminate. Of course, the invention in not limitedto any particular ionic liquid catalysts.

The alkylation process may include a regeneration zone for thein-process reactivation of at least a portion of a spent or partiallyspent ionic liquid catalyst. For example, a portion of the catalyticcomposition may be fed, in-process, to the regeneration zone. Thecatalyst composition in the regeneration zone may be regenerated bytreatment with Al metal to provide reactivated ionic liquid catalysttogether with an excess of AlCl₃, and the first catalyst precursor maybe added to the catalytic composition in an amount sufficient to providean AlCl₃/first catalyst precursor molar ratio of about two. The catalystprecursor may be coated with a hydrophobic material prior to addition ofthe catalyst precursor to the catalytic composition. In an embodiment,the regeneration conditions may be conducive to the removal of thehydrophobic material from the catalyst precursor, e.g., the temperaturein the regeneration zone may be equal to or greater than (≧) the meltingpoint of the hydrophobic material. The hydrophobic material may have amelting point in the range from about 35° C. to about 125° C., typicallyfrom about 40° C. to about 95° C., and usually from about 45° C. toabout 80° C.

The isoparaffins for the alkylation reaction may include, e.g.,isobutane, isopentanes, and mixtures thereof and the olefins mayinclude, e.g., ethylene, propylene, butylenes, pentenes, and mixturesthereof. Alkylation conditions may include a temperature of from 50° C.to 100° C., a pressure of from 300 kPA to 2500 kPa, an isoparaffin toolefin molar ratio of from 2 to 8, and a residence time of from 1 minuteto 1 hour. The ionic liquid catalytic composition may include apromoter, such as a C₂-C₆ alkyl halide, and the catalytic compositionmay further include an HCl co-catalyst.

As a non-limiting example, in an alkylation process of the presentinvention, at least one C₂ to C₆ olefin and at least one C₃ to C₆isoparaffin may be contacted in an alkylation zone under alkylationconditions with an ionic liquid catalyst to provide an alkylate. Theionic liquid catalyst may be prepared from a hygroscopic first catalystprecursor, such as salts of the general formulas A, B, C, and D (supra).In a subsequent step, the hydrocarbon phase containing the alkylate maybe separated from an ionic liquid phase comprising partially spentcatalyst. At least a portion of the partially spent catalyst may betreated with a regeneration metal to provide a reactivated catalyticcomposition with the concomitant formation of a metal halide (e.g.,AlCl₃), and the metal halide thus formed is contacted with an additionalamount of the first catalyst precursor.

In an embodiment where the first catalyst precursor is added to thecatalytic composition before or concurrently with the regenerationmetal, the metal halide formed during catalyst regeneration may reactwith the catalyst precursor in situ to form new ionic liquid catalyst.In other embodiments where the catalyst precursor is added to thecatalytic composition after treatment with the regeneration metal,excess metal halide may accumulate in the catalytic composition.Accordingly, an amount of the catalyst precursor may be added to thereactivated catalytic composition sufficient to react with the excessmetal halide to form new ionic liquid catalyst. In an embodiment,sufficient of the catalyst precursor may be added to the reactivatedcatalytic composition so as to remove at least substantially all of theexcess metal halide.

As noted hereinabove, the first- or organic catalyst precursor may becoated with one or more hydrophobic materials prior to the addition ofthe catalyst precursor to the reactivated catalytic composition. In anembodiment, the catalyst precursor may be added under regenerationconditions sufficient to remove the hydrophobic coating material fromthe first catalyst precursor. The hydrophobic coating on the catalystprecursor serves as an effective water barrier, simplifies handling ofthe catalyst precursor, and prevents the introduction of water into thecatalyst system.

EXAMPLES

The following Examples are illustrative of the present invention, butare not intended to limit the invention in any way beyond what iscontained in the claims which follow.

Example 1 Preparation of 1-Butylpyridinium Chloroaluminate Ionic LiquidCatalyst

1-butylpyridinium chloroaluminate is a room temperature ionic liquidprepared by mixing neat 1-butylpyridinium chloride (a solid) with neatsolid aluminum trichloride in an inert atmosphere. 1-butylpyridiniumchloride and the corresponding 1-butylpyridinium chloroaluminate weresynthesized as follows. In a 2-L Teflon-lined autoclave, 400 gm (5.05mol.) of anhydrous pyridine (99.9% pure, Aldrich) were mixed with 650 gm(7 mol.) of 1-chlorobutane (99.5% pure, Aldrich). The neat mixture wassealed and stirred at 125° C. under autogenic pressure overnight. Aftercooling and venting the autoclave, the reaction mix was diluted anddissolved in chloroform and transferred to a 3-L round bottom flask.Concentration of the reaction mixture at reduced pressure on a rotaryevaporator (in a hot water bath) to remove excess chloride, unreactedpyridine, and the chloroform solvent gave a tan solid product.Purification of the product was done by dissolving the obtained solidsin hot acetone and precipitating the pure product through cooling andaddition of diethyl ether. Filtering and drying under vacuum and heat ona rotary evaporator gave 750 gm (88% yields) of the desired product asan off-white shiny solid. ¹H- and ¹³C-NMR were consistent with thedesired 1-butylpyridinium chloride, and no impurities were observed.

1-butylpyridinium chloroaluminate was prepared by slowly mixing dried1-butylpyridinium chloride and anhydrous aluminum trichloride (AlCl₃)according to the following procedure. The 1-butylpyridinium chloride wasdried under vacuum at 80° C. for 48 hours to remove residual water(1-butylpyridinium chloride is hygroscopic and readily absorbs waterupon exposure to air). Five hundred grams (2.91 mol.) of the dried1-butylpyridinium chloride were transferred to a 2-L beaker in anitrogen atmosphere in a glove box. Then, 777.4 gm (5.83 mol.) ofanhydrous powdered AlCl₃ (99.99%, Aldrich) were added in small portions(while stirring) to control the temperature of the highly exothermicreaction. Once all the AlCl₃ was added, the resulting amber-lookingliquid was left to gently stir for an additional ½-1 hour. The liquidwas then filtered to remove any un-dissolved AlCl₃. The resulting acidic1-butylpyridinium chloroaluminate was used as the catalyst for thealkylation of isoparaffins with olefins.

Example 2 Preparation of Deactivated Ionic Liquid Catalyst

Deactivated or “used” ionic liquid catalyst was prepared from1-butylpyridinium chloroaluminate ionic liquid catalyst (Example 1) byperforming isobutane alkylation in a continuous flow microunit undercatalyst recycle with accelerated fouling conditions.

The microunit consists of feed pumps for isobutane and butenes, astirred autoclave reactor, a back pressure regulator, a three phaseseparator, and a third pump to recycle the separated ionic liquidcatalyst back to the reactor. The reactor was operated at 80 to 100 psigpressure and with cooling to maintain a reaction temperature of ca. 10°C. To start the reaction, isobutane, butenes, and HCl were pumped intothe autoclave at the desired molar ratio (isobutane/butenes>1.0),through the back pressure regulator, and into the three phase separator.At the same time, the chloroaluminate ionic liquid catalyst (Example 1)was pumped into the reactor at a rate pre-calculated to give the desiredcatalyst/feed ratio on a volumetric basis. As the reaction proceeded,ionic liquid separated from the reactor effluent and collected in thebottom of the three phase separator. When a sufficient level of catalysthad accumulated in the bottom of the separator, the flow of fresh ionicliquid was stopped and catalyst recycling from the bottom of theseparator was started. In this way, the initial catalyst charge wascontinually used and recycled in the process. The process conditionswere as follows: isobutane pump rate 4.6 g/min; butene pump rate 2.2g/min; catalyst pump rate 1.6 g/min; HCl flow rate 3.0 SCCM; pressure100 psig; temperature 10° C. The reaction was continued for 72 hourswhen it was judged that the catalyst had become sufficientlydeactivated.

Example 3 Quantification of Conjunct Polymer and Olefin Oligomers inDeactivated Catalyst

The wt % of conjunct polymers in the spent (deactivated) ionic liquidcatalyst was determined by hydrolysis of known weights of the spentcatalyst (prepared in Example 2). In a glove box, 15 gm of spent ionicliquid catalyst in a flask were rinsed first with 30-50 ml of anhydroushexane to remove any residual hydrocarbon or olefinic oligomers from thespent catalyst. The hexane rinse was concentrated under reduced pressureto give only 0.02 gm of yellow oil (0.13%). Then, 50 ml of anhydroushexane was added to the rinsed catalyst followed by the slow addition of15 ml of water, and the mixture was stirred at 0° C. for 15-20 minutes.The resulting mixture was diluted with an additional 30 ml of hexanesand stirred well for an additional 5-10 minutes. The mixture was allowedto settle into two layers together with some solid residue. The organiclayer was recovered by decanting. The aqueous layer was further washedwith an additional 50 ml of hexanes. The hexanes layers were combinedand dried over anhydrous MgSO₄, filtered and concentrated to give 2.5 gm(16.7 wt % of the spent catalyst) of viscous dark orange-reddish oil. Itwas determined therefore that this particular spent catalyst contains0.13% oligomers and 16.7% conjunct polymers. The hydrolysis can also beaccomplished using acidic (aqueous HCl) or basic (aqueous NaOH)solutions.

Example 4 Characterization of Conjunct Polymer Recovered fromDeactivated Catalyst

The conjunct polymers recovered according to Example 3 werecharacterized by elemental analysis and by infrared (IR), NMR, GC-MS,and UV spectroscopy. The recovered conjunct polymers have ahydrogen/carbon ratio of 1.76 and a chlorine content of 0.8%. ¹H- and¹³C-NMR spectroscopy showed the presence of olefinic protons andolefinic carbons. IR spectroscopy indicated the presence of olefinicregions and the presence of cyclic systems and substituted double bonds.GC-MS analysis showed the conjunct polymers to have molecular weightsranging from 150-mid 600s. The recovered conjunct polymers have boilingranges of 350-1100° F., as indicated by high boiling simulateddistillation analysis. UV spectroscopy showed an absorption peak(λ_(max)) at 250 nm pointing to the presence of highly conjugated doublebond systems.

Example 5 Catalyst Regeneration by Removal of Conjunct Polymers Using AlMetal

A 300 cc autoclave was charged with 51 gm of used (deactivated)1-butylpyridinium chloroaluminate ionic liquid containing 15.5 wt %(7.90 gm) conjunct polymers, 65 ml of hexane, and 8 gm of aluminumpowder. The autoclave was heated to 100° C. while stirring with anoverhead stirrer at 1200 rpm. The starting autogenic pressure of thereaction was 11 psi and rose to 62 psi (at 100° C.) and remained therefor the duration of the reaction. The reaction was allowed to run for1.5 hrs. The reaction was cooled down, and the reaction mixture wasseparated in a glove box where the hexane layer was removed bydecantation. The ionic liquid/Al metal residue was rinsed twice (2×)with 50 ml of anhydrous hexane. The hexane layers were all combined anddried over MgSO₄. Filtration and concentration of the dried hexanerinses gave 6.3 gm (99.7%) of the expected conjunct polymers as paleyellow oils. The ionic liquid catalyst was separated from aluminum byfiltration. Hydrolysis of a 10 gm portion of the filtered ionic liquidcatalyst, followed by extraction with hexane, showed no presence ofconjunct polymers in the treated spent ionic liquid.

The reaction described above was repeated using the same sample of spentcatalyst, resulting in the removal of >98% of the conjunct polymers. Thereaction was repeated on 52 gm of spent butylpyridinium chloroaluminatecatalyst containing 15.5 wt % (7.9 gm) of conjunct polymer, resulting inthe removal of 7.75 gm (98.0%) of the conjunct polymers from the spentcatalyst. Hydrolysis of the regenerated ionic liquid catalyst indicatedthe presence of <0.5% of conjunct polymers.

Example 6 Catalyst Regeneration Using Zn, In, or Ga Metal

The catalyst regeneration procedure of Example 5 was repeated usingeither excess zinc, indium, or gallium metal (8 grams in each case)instead of Al metal to regenerate spent ionic liquid (ca. 50 gm in eachcase) containing 24.3 wt % conjunct polymers. The reactions ran for 1.5hours at 100° C., after which treatment with Zn, In, and Ga was found toprovide 81%, 89%, and 45% removal, respectively, of the conjunctpolymers present in the spent catalyst.

Example 7 Regeneration of Spent Catalyst Prior to Addition of CatalystPrecursor

Spent catalyst containing conjunct polymer was regenerated with Al metalprior to the addition of organic catalyst precursor (1-butylpyridiniumchloride) as follows. A 300 cc autoclave equipped with an overheadstirrer was charged with 100 gm of spent ionic liquid containing 24 wt %conjunct polymers, 8 gm of aluminum powder, and 60 gm of n-hexane. Theautoclave was sealed, heated to 100° C., and allowed to stir at maximumspeed (ca. 1600 rpm) for 90 minutes. Then, the reaction was cooled toroom temperature. The reaction mixture was allowed to settle and thehydrocarbon (top) layer was decanted. The ionic liquid layer togetherwith the Al metal powder was rinsed twice with anhydrous n-hexane andall of the hexane fractions were combined and the hexane removed torecover the conjunct polymers. The ionic liquid layer containing the Almetal was filtered in a glove box (inert atmosphere) to separate theregenerated ionic liquid catalyst from the Al metal.

The regenerated ionic liquid catalyst, 65 gm, appeared as a transparentamber solution. This ionic liquid catalyst was allowed to stand at roomtemperature for a few hours, after which it turned from transparent toopaque. After standing at room temperature overnight, the ionic liquidbecame transparent with the appearance of an AlCl₃ precipitate at thebottom. To this solution, 1 gm of 1-butylpyridinium chloride was addedto react with the precipitated AlCl₃ and the mixture was stirred for afew minutes at room temperature. The AlCl₃ precipitate disappeared, andafter standing at room temperature over the weekend no furtherprecipitation occurred nor did the ionic liquid lose its transparency.The added 1-butylpyridinium chloride reacted with the excess AlCl₃ toform additional ionic liquid catalyst.

Example 8 Regeneration of Spent Catalyst in the Presence of CatalystPrecursor

A 300 cc autoclave equipped with an overhead stirrer was charged with100 gm of spent ionic liquid containing 24 wt % conjunct polymers, 8 gmof aluminum powder, 1.5 gm of 1-butylpyridinium chloride, and 60 gm ofn-hexane. As in Example 7, the autoclave was sealed, heated to 100° C.,and allowed to stir at maximum speed (ca. 1600 rpm) for 90 minutes,after which the reaction was cooled to room temperature. Again as inExample 7, the reaction mixture was allowed to settle and thehydrocarbon (top) layer was separated from the ionic liquid and Al metalby decanting the top layer. The ionic liquid layer with the Al powderwas rinsed twice with anhydrous n-hexane and all of the hexane fractionswere combined, and then the hexane was removed to recover the conjunctpolymers. The ionic liquid layer containing the Al powder was filteredin a glove box (inert atmosphere) to separate the regenerated ionicliquid catalyst from the Al metal. The resulting regenerated ionicliquid catalyst, 68 gm, appeared as a transparent amber solution. Unlikethe regenerated catalyst obtained in Example 7, the catalyst did notbecome opaque on standing at room temperature for several days, and noAlCl₃ precipitate was observed after standing at room temperature fortwo weeks. The inclusion of 1-butylpyridinium chloride from the start ofthe regeneration process allowed the 1-butylpyridinium chloride tointeract in situ with the AlCl₃ produced by catalyst regeneration toform new ionic liquid catalyst.

Numerous variations of the present invention may be possible in light ofthe teachings and examples herein. It is therefore understood thatwithin the scope of the following claims, the invention may be practicedotherwise than as specifically described or exemplified herein.

1. A method for stabilizing a catalytic composition, the methodcomprising: the in-process addition of a hygroscopic catalyst precursorto the catalytic composition in an amount effective to control thecatalytic activity of the catalytic composition, wherein the catalystprecursor is at least partially encapsulated within a hydrophobicmaterial prior to the addition of the catalyst precursor to thecatalytic composition.
 2. The method according to claim 1, wherein thecatalytic composition comprises an acidic ionic liquid catalyst.
 3. Themethod according to claim 1, wherein the catalyst precursor is selectedfrom the group consisting of salts of the general formulas A, B, C, andD:

wherein X is halide, each of R, R₁, and R₂=H, methyl, ethyl, propyl,butyl, pentyl or hexyl, wherein R₁ and R₂ may or may not be the same;and each of R₃, R₄, R₅, and R₆=methyl, ethyl, propyl, butyl, pentyl orhexyl, wherein R₃, R₄, R₅, and R₆ may or may not be the same.
 4. Themethod according to claim 2, wherein the ionic liquid catalyst isprepared by contacting the catalyst precursor with aluminum trichloride(AlCl₃) in an AlCl₃/catalyst precursor molar ratio of about
 2. 5. Themethod according to claim 1, wherein the catalytic composition containsan excess of aluminum trichloride, and the catalyst precursor is addedto the catalytic composition in an amount sufficient to provide anAlCl₃/catalyst precursor molar ratio of about
 2. 6. The method accordingto claim 1, wherein the catalyst precursor is pelletized to form pelletsof the catalyst precursor, and the pellets are coated with thehydrophobic material to provide moisture resistant granules of thecatalyst precursor.
 7. The method according to claim 6, wherein thegranules of catalyst precursor comprise a pelletized 1-alkylpyridiniumchloride coated with wax.
 8. The method according to claim 1, whereinthe catalyst precursor is added to the catalytic composition underconditions sufficient to at least partially remove the hydrophobicmaterial from the catalyst precursor.
 9. The method according to claim1, wherein the hydrophobic material has a melting point less than about100° C.
 10. The method according to claim 1, wherein the hydrophobicmaterial is soluble in C₃ to C₁₅ hydrocarbons.
 11. The method accordingto claim 1, wherein the hydrophobic material comprises a paraffin wax.12. A method for stabilizing a catalytic composition, the methodcomprising: adding a first catalyst precursor to a catalyst regenerationzone; and forming an ionic liquid catalyst de novo in the regenerationzone by contacting the first catalyst precursor with a second catalystprecursor, wherein the first catalyst precursor is coated with ahydrophobic material prior to the addition of the first catalystprecursor to the regeneration zone.
 13. The method according to claim12, wherein the first catalyst precursor is selected from the groupconsisting of salts of the general formulas A, B, C, and D:

wherein X is halide, each of R, R₁, and R₂=H, methyl, ethyl, propyl,butyl, pentyl or hexyl, wherein R₁ and R₂ may or may not be the same;and each of R₃, R₄, R₅, and R₆=methyl, ethyl, propyl, butyl, pentyl orhexyl, wherein R₃, R₄, R₅, and R₆ may or may not be the same.
 14. Themethod according to claim 12, wherein the second catalyst precursor isformed in the regeneration zone by treating a spent catalyst with aregeneration metal.
 15. The method according to claim 12, wherein thesecond catalyst precursor comprises AlCl₃, and the first catalystprecursor is added to the catalytic composition in an amount sufficientto provide an AlCl₃/first catalyst precursor molar ratio of about
 2. 16.The method according to claim 12, wherein the regeneration zone is at atemperature equal to or greater than the melting point of thehydrophobic material.
 17. The method according to claim 12, wherein thehydrophobic material comprises a paraffin wax having a melting point inthe range from about 40° C. to about 95° C.
 18. A method for stabilizinga catalytic process, the method comprising: a) separating a partiallyspent ionic liquid catalyst from a reaction product; b) feeding aportion of the partially spent catalyst to a regeneration zone, whereinthe partially spent ionic liquid catalyst includes bound conjunctpolymer; c) contacting the partially spent catalyst with aluminum metalunder regeneration conditions to provide a catalytic compositioncomprising i) reactivated ionic liquid catalyst and ii) free conjunctpolymer, wherein AlCl₃ is formed by reaction of the aluminum metal withthe partially spent catalyst; d) adding an organic catalyst precursor tothe catalytic composition; and e) forming the ionic liquid catalyst denovo by reacting the catalyst precursor with the AlCl₃, wherein thecatalyst precursor is at least partially coated with a hydrophobicmaterial prior to the adding step.
 19. The method according to claim 18,wherein the coated catalyst precursor is added to the catalyticcomposition prior to, concurrently with, or subsequent to the contactingstep.
 20. The method according to claim 18, wherein the catalystprecursor is selected from the group consisting of salts of the generalformulas A, B, C, and D:

wherein X is halide, each of R, R₁, and R₂=H, methyl, ethyl, propyl,butyl, pentyl or hexyl, wherein R₁ and R₂ may or may not be the same;and each of R₃, R₄, R₅, and R₆=methyl, ethyl, propyl, butyl, pentyl orhexyl, wherein R₃, R₄, R₅, and R₆ may or may not be the same, andwherein the catalyst precursor is added to the catalytic composition inan amount sufficient to provide an AlCl₃/catalyst precursor molar ratioof about 2.